Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 15, 2003
Publication Date: September 1, 2003
Citation: Adhikari, T.B., Anderson, J.M., Goodwin, S.B. 2003. Identification and molecular mapping of a gene in wheat conferring resistance to Mycosphaerella graminicola. Phytopathology. 93:1158-1164. Interpretive Summary: Septoria tritici leaf blotch (STB), caused by the fungus Mycosphaerella graminicola (Septoria tritici is the name for its asexual stage), is an economically important disease in most of the major wheat-growing areas worldwide. Breeding for resistance to STB, the most effective means to control this disease, is time consuming and labor intensive, but can be facilitated greatly through the use of molecular markers. However, molecular markers linked to most genes for resistance to STB are not yet available. This study was conducted to test for resistance in the parents of a standard wheat mapping population and to map any resistance genes identified. Genetic analysis indicated that a single major gene controls the resistance to M. graminicola. Two molecular markers are closely linked on either side of the resistance gene, so can be useful for moving the gene into improved wheat cultivars. This putative resistance gene is different from those that have been mapped previously and appears to be new, so was designated Stb7. This information will be of great interest to plant pathologists trying to manage this disease, as it confirms the existence of another specific interaction between M. graminicola and host resistance genes. Plant breeders worldwide can use the molecular markers to select resistant individuals rather than performing inoculations. This will permit selection at the two-leaf stage which will be much faster and easier compared to growing the plants to maturity and inoculating with the pathogen. This should speed up the breeding process by several months each year which will decrease costs. These markers will allow this new source of resistance to be utilized immediately to its maximum potential.
Technical Abstract: Septoria tritici leaf blotch (STB), caused by the ascomycete Mycosphaerella graminicola (anamorph Septoria tritici), is an economically important disease of wheat. Breeding for resistance to STB, the most effective means to control this disease, can be facilitated through the use of molecular markers. However, molecular markers linked to most genes for resistance to STB are not yet available. This study was conducted to test for resistance in the parents of a standard wheat mapping population and to map any resistance genes identified. The population consisted of 130 F10 recombinant inbred lines (RILs) from a cross between the synthetic hexaploid wheat W7984 and the cultivar Opata 85. Genetic analysis indicated that a single major gene controls the resistance to M. graminicola. This putative resistance gene was designated Stb7, and was mapped with respect to amplified fragment length polymorphism (AFLP) and microsatellite markers. An AFLP marker, EcoRI-ACG/MseI-CAG5, was linked in repulsion with the resistance gene at a distance of approximately 5.3 centimorgans (cM). Two flanking microsatellite markers, Xgwm146 and Xgwm577, were linked to the Stb7 gene on the long arm of wheat chromosome 7B at distances of 3.5 and 5.3 cM, respectively. The microsatellite markers identified in this study have potential for use in marker-assisted selection in breeding programs and for pyramiding of Stb7 with other genes for resistance to M. graminicola in wheat.